rests, & esp. sandbags

C

Charles E

curmudgeon
Has anyone ever experimented with making rests, esp. "sandbags" that are outside the rules, but might give useful information?

Here is something I've noticed from shooting score, both rimfire, where I'm a neophyte, and centerfire, where I'm not:

As you move round the target, strange things happen. By "strange," I mean the shot doesn't go where you would think it would.

I'd say it doesn't go where expected, except this is so repeatable that you can hold for it, and while you're holding in a different place for a X, you get the X.

The main problem: I have this happen in CF esp. on the top two bulls, and in RF on the two right columns, where (on the IBS target) there is no sighter bull above the record bulls. In other words, in both RF and CF score, the shots on the bulls farthest away from the sighters where you initially set up, repeatably show different points of impact from the record bulls closest to the sighter bull.

I've also read all the differing theories I could find on the best material and filll for good sandbags. Heavy sand for weight, Sand with irregular edges. Etc. Looser packed, hard packed, various tension from the rest on the front bag, on & on.

Read what I could find on the proper shape for the rear bag. Boyd Allen has done some testing on the shape of the rear bag, but I think he's formed no firm conclusions. He and others have experimented with how the butt contacts the ears and bottom of the rear bag.

Best I can tell, there is no repeatable, works-on-all-rifles setup, with the possible exception of unlimiteds -- which with score, is only shot in rimfire..

* * *

I hope I've described the problem well enough. Here is the thinking:

We could make "sandbags" out of foam rubber, or hard rubber, or a combination of foam & hard rubber. Or something else. Pretty much any shape, stiffness, contact area, etc. we'd like to try. Anybody tried this and come up with superior, repeatable results? It wouldn't be legal, except for shooting a bag gun in the unlimited class, but might teach us a whole lot about how to make better legal sandbag/rests.
 
'Morning, Charles. You've touched on one of the most important, yet least appreciated, aspects of Score shooting.

The gun simply must not change p.o.i. as it's moved around the Score target. This isn't always as easy as it first appears and depends on the entire combination of bag(s), rest, rest top angle, rear bag, bag hardness, stock, etc, etc. Some combinations of front rests and stocks are more forgiving in this respect and some can be a bit more snotty.

Here's some interesting numbers from the IBS 100 yd. Score target. Starting @ the center of the sighter and going up and around to the center of each bull, here's how much movement happens:
Sighter to #5:- 7"
#5 to #4- 5 3/8"
#4 to #3 -crossover 5.5" and down 1.5" for 7" total movement
#3 to #2- 5 3/8"
#2 to #1- 5 3/8"
Total movement: 30 1/8". And that's just the 100 yd. target.

That a great Score setup can move from any bull to the sighter and back again w/o changing p.o.i. is mostly overlooked by other disciplines. ;)

To your question, a windage adjustable rear bag holder could make the crossover process more forgiving but it's outside the rules. As Nenderthal as it sounds, I'll at times physically move the rear bag to the left when I crossover, depending on what front rest top I'm using. My Ron Hoehn windage top setup for my HBR gun is more forgiving than the setup I have on the Farley rest for the VfS gun. I've got a Hoehn top for the VfS guns and the more I use the Farley, the more I like Ron's tops.

Good shootin'. -Al
 
As I read this it brings to mind a theory I have had for some years but unable to confirm.
2 forms of shooters ones who move the front rest and those who bag squeeze.
I am only addressing the movable front rest.
We tend to have the front end restricted except for front to rear motion, some tighter than others.
The rear bag while having no great tension is basically designed for the gun to move on forward and backward.
Any time we set the gun up for a perfect return to the same exact aim point AND THEN begin moving the front rest from side to side we have skewed the plane that the gun was set up to travel on thereby adding a type of torque, or binging (whatever word works) to the set up, putting uneven pressure on the gun either on front, back or both and on opposite sides.
For group this does not seem to be near the issue it is for score except when you begin to try and hold off, but usually not that far.
For score as you have both noted you move all over the target and from right to left as much as 6".
It would seem if the front and rear setup could be kept/fixed and moved on the same plane at the same time it might solve part of the issue but we all know at this point that would never be allowed in the rules.
In other words windage adjustment moves both front and rear the same amount at the same time.
Just a thought.
 
Let me suggest a place to start. Start with a flexible rear and front bag. Fill them with something light and soft, like Styrofoam pellets or plastic pellets. This will create a suspension platform for the stock that has very little effect on stock vibration. Seriously!!
 
Just a note to Al -- Interesting preference. If you have an Edgewood bag for the Farley, even more so. Both the Farley/Edgewood and Hohen have a wide, flat "bottom" for the forearm to rest on. The main difference is the Hohen puts whatever pressure it puts on the sides of the forearm quite low, whereas the Farley/Edgewood puts pressure rather higher up.

BTW, there is a top used by some rimfire guys that will move (rotate), very easily in the horizontal plane. It also has independent contacts for bottom and sides. They are round, and quite small (and quite hard), but I think would be legal in CF. I saw one last weekend, for the first time.

Which was interesting, as I've been thinking that a roundish bag might be better.

Jerry's notion is interesting too. But as long as we're going to start illegal, I thought close-coat foam might be better, as that will allow for easy adjustment to the shape to boot.
 
Francis, just to be perfectly clear -- where have we heard that before -- I'm not interested in or advocating using an illegal bag. I'm interested in finding out what works, so when we -- I -- have to deal with leather and sand, life becomes easier cutting & sewing.
 
In many cases what use to be illegal was examined and changes were made to existing rules to make what was once illegal now legal.
Tuners, donuts, skeletonized stocks, just to name a few.
We never know until we do some testing and think outside the box.
 
Let me propose a test that I have yet to do, but which I am getting closer to. Protektor Model makes a front bag with no ears. Start with that, and combine it with my little idea as to how to rapidly reposition your rifle in the center of it. Take a piece of thin hobby plywood, Micarta, or aluminum, cut to a width that will allow fall within the 3" rule with tape, and to a length of about 6-7 inches, then cut a V in what will be the front side, that is the full width of the side, and which forms a 60 to 90 degree angle. You will need a conventional round forend stop set so that when it is within the bottom of the V, your rifle is centered on the front bag, and in the desired position front to back. Tape the V plate to the stock so that the entire depth of the V is in front of the forend. When shooting, push the rifle forward till the V centers the forend on the bag, and then back it up out of contact with the stop a small amount. The point of the exercise is to let the rifle slide where ever it will front to back and sideways, as it recoils, while being able to reacquire your point of aim rapidly. Out of the box and I are old friends. I have the plywood, and the tape, and will probably use double stick tape on top of my existing tape to insure that I don't damage my paint job. Comments? Suggestions for medication?
 
I think some of the issues could be minimized by the use of the Randolf rest as the top rotates freely and eliminates any and all pinching issues with the forearm when moving in the horizontal plane. One cannot help but think this would also be helpful to minimize the issues of the back bag tracking as well. The rest is a work of mechanical perfection yet I don't hear of its use being mentioned as much I would expect it to.

J.Louis
 
And now for something completely different :)

(Or maybe not, I THINK I'm with Sharrett)

In my limited experience I've found two kind of guns, those that will shoot free recoil and those that won't.

I only trust those that will.

I'll cite the example of my Borden TPE heavy PPC. AS BUILT by Jim, he balanced it and set it up scope and all, it'll shoot any way you want it. You want to set it on a pickup hood and stand back and throw rocks at it until it fires, IT WILL SHOOT..... But I've messed with it. I've added barrels and adjustable weights and otherwise modified it to shoot as a 6X47L for 600yd use. And won some local wood. But with my modifications it's icky-sticky-picky. I WILL STILL SHOOT but only if it's set up just so. And if I lose it during a string I'm boned.

I can screw one of several 6PPC barrels back on, put it back to Jim's settings and it's like riding Ol' Flossie, point and shoot. Crank the Fartley over to another paper and shoot some more.....easy-peasy.

I set up my 30X47L this way. It's taken some serious barrel(s) time but I don't spend hours agonizing about bag hardness, ear tension, spring tension, side tension, lubrication, overhang, height, weight distribution, humidity, temperature, the state of my facial hair........ It's now just point and shoot, no drama.

I've been building some hunting rifles. My current theory is that they MUST shoot free recoil off the bipod. This is hard to get, but once it's GOT the guns just shoot any old way you flop them.

In short, I'm currently of the belief that "tracking" has to be considered as a "Space Problem" not a guiding means problem.

I think Charles has opened a really big worm can here........... PLEASE OPINE FOLKS!!!

Keep it coming


al
 
On the theory that shooting doesn't involve magic, with Al's (inwa, not Nyhus) notion, the testing should be to start adding weight hither & yon, for balance purposes only, until bags don't seem to matter.

Once you have that ratio, then test to make sure it is a general principle, something that doesn't vary from rifle to rifle, except, perhaps, for a few ounces -- like tuning a load.

Now cut & add weight until it's legal.

While I wouldn't rule it out, I'm not hopeful. The other thing would be for Al to shoot a rimfire target -- 25 spaced-out bulls with a .062 dot -- and see if his observation holds up on that scale of things. We need over 20 Xs on that target, Al.

* * *

The Randolf -- AKA Fulgham -- rest is indeed a wonderful piece of machinery -- I've seen, but not used one. The top, available separately, is something like what I have in mind

http://www.randolphmachine.com/atop.html

The top I'm thinking looks a lot like this, but has a plate on top of all the adjustments that will rotate -- sort of spin -- quite freely in the horizontal position, but is dead-nuts stable vertically. With my thinking, that lack of vertical motion might be good, or bad. The "bag" is round and quite hard, so the infamous "edge of sand" might not build up as the rifle is shot & returned to battery.

The other way to think about all this is Vaughn-like. All we really want is for the barrel to be returned to battery, in a slightly new position, with exactly the same loading on it as previous. All this stiffness everywhere is the real can of worms. The best way to go is to get rid of the effect of the stock on the barreled action. Make it's relation, and the bags, & rest, & all of that other stuff irrelevant. Get rid of the stock & fuss with the bags, or make the bedding itself "on air." Might be easier that way. AKA Gene Beggs design, with a little more freedom in the butt (don't take that sentence out of context & throw it at Gene, please.)

Keep it coming. Any more secrets to share, Al (Nyhus)? Or flat out actual tests Al (inwa)? Or anyone else who's seen & worked on this phenomena & is willing to help people who just want to beat him next time out?
 
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Charles, a magnetic base protractor ($10 Craftsman) out near the muzzle can be an eye opener. Set up the front rest and rear bag, then tinker as you go around a target, noting the changes on the protractor. Keeping the relationship (contact area) between the bottom of the fore end and the front bag as constant as possible as the gun is moved is, in my opinion, one of the biggest things to work on.

I spent a lot of time this season working with my 6PPC. When I set the gun/rest/bag up as is commonly done, my first shot on the record target when going up from the sighter (Group target) popped up high over 25% of the time. After a while, I got the hang of holding higher for the second shot when this happened, but it always gave me the heebie jeebies to do this. Being primarily a dirt clod Score shooter, I simply went back to the ways of the Great Unwashed. The first shot never popped high again.

Once a dirt clod, always a dirt clod. :eek: -Al
 
Al, I will pass on commenting on shooting lightweight magnums in hunting stocks free, bipod or no, but the thing about heavy 6PPCs is the recoil to rifle weight. IMO that is why Ratigan describes shooting a .100 short .22 PPC as so easy it is like cheating. I too like bench rifles to be balanced, stocked and bagged to be able to be shot free, but if the stock is not right, the balance is not there, and the recoil to rifle weight is not in the range, IMO you are wasting your time. All in all everything get easier as you add weight, if you keep everything else constant. I wouldn't think that balancing a heavy, that was built from the ground up as a heavy, would be that big of a trick, a sporter/light in 6PPC is another matter.
 
Boyd Allen said:
Al, I will pass on commenting on shooting lightweight magnums in hunting stocks free, bipod or no, but the thing about heavy 6PPCs is the recoil to rifle weight. IMO that is why Ratigan describes shooting a .100 short .22 PPC as so easy it is like cheating. I too like bench rifles to be balanced, stocked and bagged to be able to be shot free, but if the stock is not right, the balance is not there, and the recoil to rifle weight is not in the range, IMO you are wasting your time. All in all everything get easier as you add weight, if you keep everything else constant. I wouldn't think that balancing a heavy, that was built from the ground up as a heavy, would be that big of a trick, a sporter/light in 6PPC is another matter.
Click to expand...

As you well know Boyd, time is a valuable commodity and we all must pick our projects so not ALL testing has been done, but maybe you missed the part about a 10lb 308 :) ??? My score gun is very tractable.

It IS possible to free recoil high power-to-weight-ratio rifles....just, as you rightly point out, hard to achieve. BTW my Borden 10.5 PPC also shoots free recoil. Only I haven't hacked it all up yet so I didn't use it to illustrate my point.

Of course the 338 we've been discussing is in a whole different frame-twisting space-time warping league of it's own! Big power brings in another whole set of problems.

al
 
alinwa said:
... Of course the 338 we've been discussing is in a whole different frame-twisting space-time warping league of it's own! Big power brings in another whole set of problems.
Click to expand...
With my .338 Light Gun, I am occasionally bloodied, but as yet unscarred.

However, yes, just now, I'm interested in rifles in the .22 rimfire to .30 BR range.
 
G'day

Can I ask if the butt of the stocks you are using are flat (parrallel to the forend) or the more traditional angled???

Thankyou for your time.

harro
 
Depends. My 1K rifles are usually parallel. My new RF is going to be as well, when I get to it. Current RF is in a left-over centerfire BR stock, and like my other CF BR stocks, is tapered to meet the rules.

Actually, as we've been shooting 1K BR for almost 16 years now, there is a faction that thinks the butt should be almost, but not quite parallel. Believe both Bill Shehane's and Dave Tooley's (through the McMillan MBR) stocks follow this thinking. Reason given is a bit of taper helps the butt release.

With IBS and NBRSA score shooting, the regular HV taper rules apply.
 
Gentlemen: After following your comments, I couldn't help but remember an article I had read in the February 2010 issue of Precision Shooting. The article, written by John W. Lewis is entitled Front Rests.

The issue of overcoming any tendency for the rest to cause a vertical shift when going from the sighter target the record target is discussed, as well as rear bag design, and the use of the fuzzy side of Velcro on the front and rear bags.

The really good stuff starts on page 84, with Larry Feusse, Joel Kendrick, and Wayne Campbell fixes for elevation changes.
 
abintx said:
Gentlemen: After following your comments, I couldn't help but remember an article I had read in the February 2010 issue of Precision Shooting. The article, written by John W. Lewis is entitled Front Rests.

The issue of overcoming any tendency for the rest to cause a vertical shift when going from the sighter target the record target is discussed, as well as rear bag design, and the use of the fuzzy side of Velcro on the front and rear bags.
Click to expand...

Thanks for the tip, I found the magazine, I'll read it tonight.
G.
 
The fuzzy side of velcro works great.... even better than nylon if it can be incorporated in your set-up. Seems to not attract moisture even better than nylon and releases with very little break-a-way force. If somebody could line rabbit ears with it would probably make a big hit for some disciplines. Some people use dryer sheets laid on the rear bag ears to similar affect.
Many mechanical rests for precision rimfire shooting have incorporated velcro for years.
 
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